Grate



March 11, 1941. w. A. RIDDELL GRATE Filed Feb. 1, 1939 3 Sheets-Sheet v INVENTOR- 6L, MAME,

ATTORNEY @QW JN W March 11, 1941. w. A. RIDDELL 2,234,199-

GRATE Filed Feb. 1, 1959 3 Sheets-Sheet 2 Ixw- E BY Gift; ATYDORNEY March 11, 1941.

w. A. RIDDELL 2,234,199

GRATE s Sheets-Shet 3 Filed Feb. 1. 1939 IN V EN TOR.

a. awawa,

' A.TTORNEY 7 Patented Mar. 11, 1941 UNITED STATES PATENT OFFICE GRATE Application February 1, 1939, Serial No. 254,130

7 Claims.

My invention relates broadly to stoker furnaces and more particularly to an improved construction of extension grate for multiple retort underfeed stoker furnaces.

One of the objects of my invention is to provide a construction of extension grate constituted by a plurality of readily replaceable grate bar castings supported adjacent :the lower extremity of the tuyeres to support the burned mass of the firebed as it advances thereto from the main grate.

Another object of my invention is to provide a construction of stationary grate bar for extension grates formed by a single casting adapted to be replaceably mounted in position between a lower support and the lower end of a furnace grate in which the casting is so shaped and dimensioned that it will remain relatively cool under conditions of combustion and under the action of forced draft through apertures in the surface of the grate and around the side walls of the grate bar.

Still another object of my invention is to provide a construction of an extension grate bar casting having relatively high strength and shaped and dimensioned so that it may be replaceably supported in an inclined position while maintaining a condition of balanced equilibrium.

Another object of my invention is to provide a construction of stationary extension grate inclined at such an angle with respect to the horizontal that clinkers, coke and unburned fuel moving from the main grate are subjected to combustion but gravitate without accumulation on the extension grate.

A further object of my invention is to provide a construction of cast bar for extension grates having a shape corresponding substantially to an inverted channel-like member with intermediate side portions projecting normal to the active surface of the grate bar and tapering toward each end of the grate bar for imparting strength and rigidity to the inverted channel-like construction.

A still further object of my invention is to provide a construction of extension grate constituted by a plurality of substantially channel-like castings with transversely extending projections on opposite sides thereof adapted to abut with similar projections on coacting adjacent grate bars forming draft passages therebetween and wherein the external side walls of, the channel-like members are tapered to provide passages interconnecting the aforementioned passages for forced draft through the extension grate.

Another object of my invention is to provide a construction of extension grate in which the individual grate bars are provided with coacting abutments which serve to transversely align and W space adjacent grate bars and provide interme- 6 diate apertures therebetween through which draft is forced for supporting combustion on the extension grate.

Other and further objects of my invention reside in a simplified construction of stationary extension grate which may be readily manufactured at low cost and in which the maintenance cost over a long period of years is relatively low as set forth more fully in the specification hereinafter following by reference to the accompanying draw- 5 ings, in which:

Figure 1 schematically shows the application of the extension grate of my invention to stoker furnaces, the View being taken partially in elevation and partially in section to show the relative arrangement of the extension grate of my invention with respect to the main grate and the associated parts of the furnace structure; Fig. 2 is a front elevational view of the extension grate of my invention shown in position with respect to the lower grate; Fig. 3 is a transverse sectional view taken on line 3-3 of Fig. 2; Fig. 4 is a longitudinal sectional view taken through the grate bar shown on line 4-4 of Fig. 5; Fig. 5 is a top plan View of the extension grate bar shown in Fig. 4; Fig. 6 is a bottom plan view of the extension grate bar shown in Fig. 4; Fig. 7 is a side elevational View of the extension grate bar in Fig. 4; Fig. 8 is a transverse view through the extension grate bar taken on line 8-8 of Fig. 4 and illustrating the lower supporting portions of the grate bar in elevation; Fig. 9 is a transverse sectional view taken on line 9-9 of Fig. 4; and Fig. 10 is an elevational view of one of the side plates which constitute protective means for the opposite furnace walls in the extension grate assembly.

The extension grate of my invention has proven highly successful and satisfactory in actual operation in stoker furnaces in large power plants. 45 Using the extension grate of the construction set forth herein, increase in the operation eificiency of large stoker furnaces has been secured and re lacement costs due to burning out of grate 50 bars has been remarkably low. In developing the extension grate bar of the present invention, I have constructed and tested several forms of extension grates over which the present construction has proven superior in all respects.

The construction of the extension grate of my invention will be more fully understood by detailed reference to the drawings in which reference character I designates the lower extremity of the main grate of the stoker furnace. The tuyres forming part of the main grate are shown at 2. Reference character 3 indicates generally the protective plate which extends adjacent the side wall of the firebox of the furnace. I have schematically shown the supporting structures 4 and 5 extending transversely within the furnace for. mounting the extension grate of my invention in position. The extension grate is shown generally at 6 of parallel extending grate bars 1 shown. more clearly in Figs. 2 and 3. Each extension grate bar is constituted by a casting substantially in the shape of an inverted channel member having depending side walls 8. The dimensions and shape of the grate bar. are such that the bars when arranged in inclined position which is their normal positionbeneath the lower edge I of the main grate, are'ina state of substantially balanced equilibrium. The upper end of each extension grate bar terminates in a portion 9 which extends at an obtuse angle 7 (indicated in Fig. 4) with respect to the plane of the active surface of the extension grate bar which I have indicated at Ill. The channel shaped end of the portion 9 is recessed at I l and ofiers minimum obstruction to the passage of forced draft through the ex-tensiongrate. The underside of the upper extremity of the grate bar I is additionally recessed at l2 to afford maximum clearance for the passage of air through the upper slot I4 of the extension grate bar. The extension grate bar includes a plurality of downwardly extending slot is indicated at IT through which air is forced unobstructed over] the lowermost portion of the The lower end of the extension extension grate. rate bar 6 is bifurcated as indicated at 18 forming supporting projections which extend in a plane substantially at an acute'angle 5 (indicated in Fig. 4) with respectto the surface ill in a substantially lower extremity of the grate bar and is spaced peripheral edges of the lower grate bars 22 shown generally in Figs. 1 and 2.

The upper extremity of the extending grate bars constituted by the rearwardly or outwardly 5 extending portion 9 is supported by transversely 1 extending member 23 shown 1 as suported at opposite ends l are in turn mounted on generally. in Fig. 1

the transversely extending supports shown schematically at 4. The ex- 1 tension grate bars have their side Walls 8 extending to a maximum depth in a position substantially opposite the center of equilibrium of the H extension grate bar.

: the center of equilibriumof the grate bar toward each end thereof as indicated at tapered portions intersecting at an'apex portion 2! on an axis passing substantially through the The side walls 8 taper from the maximum, dimension substantially opposite 25 and 26, the

center ofequilibrium of the extension grate bar,

and consists of a plurality plete position of support on substantially 'down-' wardly extending webs l5 cast integrally inter H) of the grate bar 1. A lug member 20 projects substantially parallel to i I the bifurcated projections central position adjacent the underside of the by piers 24 which j greater than the'pitch of the main grateso that beyond the end Each extension grate bar is provided with laterally extending lugs 23 which abut with coacting lugs on adjacent extension grate bars to provide intermediate air passages 29 located between adjacent extension grate bars. In order to alford minimum obstruction to the passage of a forced draft of air through the adjacent extension grate bars, .the external side walls 8 of each extension grate bar are tapered inwardly toward the center axis of each bar. I have shown the tapered portion of the grate bars at 30 in Figs. 3, 6, 7 and 9.

'The tapering of the side walls 8 of the adjacent extension grate bars reduces the obstruction to the passage of a forced draft between the grate bars and through the passages 29. That is to say, material forming the side walls of the extension grate bars is cut away to offer minimum resistance to the passage of the forced draft.

The extension grate bars are readily replaceable by a simple angular and horizontal movement of the bars into position. After each bar is slid horizontally into posiiton with the portion 9 partially supported on transverse member'23,

the extension grate bar may be tilted upwardly a small amount until the notch 2| in the lower end thereof engages over the upwardly projecting end of lower grate bars 22 and then the upper.

ends of the extension grate bars slide to a comtransverse member 23, whereby the extension grate bars are maintained in position. It will be noted that when the grate bars are placed in final position, they remain in set position by virtue of the weight distribution therein afiorded'particularly by the extended side Walls 8, the eifect of which is a lowering of the center of equilibrium and a more stable grate assembly. The extended side walls 8, tapered as described,',therefore' cooperate in respect to both the structuraland the operational features of the extension In Fig. 1 I have shown the relationship of the lower grate bars 22 to theclinker crushing mechanism and the air-back and boiler tubes. The clinker crushing mechanism is constituted by the reciprocating crushesshown generally at 3|, and the coaoting rotary crushers shown generally at 32. The airback is illustrated schematically at 33 and the boiler tubes are shown generally at 34.

When the extension grate bars are assembled in position, it is unnecessary to provide interconnecting tie rods between the bars. However at each end of the extension grate bars, I provide a protective plate 35 which separates the side wall of the furnace from the grate. -The lugs 28 on the extension grate bars immediately adjacent the side plates 35 which air is forced.

The extension grate bars are arranged in an inclined plane so cated at H] is disposed at such an angle that clinkers and coke or semi-burned coal will not repose or accumulate to any substantial degree on the grate but will be subjected to complete combustion and tend to tumble or roll oiT the grate. That is to say, substantially all of the benefits of complete combustion are obtained and the coke,

clinkers, semi-burned coal and ashes progressive-' sion gratev makes with the horizontal plane is of approximately The pitch of'the extension grate is substantially within the range after the semi-burned fuel passes that the active surface indiprovide apertures 29 through of the main grate, further combustion is effected and thereby the thermal efl'iciency of the furnace increased without the accumulation of the semiburned fuel on the extension grate.

The width of the side walls of each of the channel shaped grate bars and the width of the webs between the grate apertures or passages '5 are selected to present a substantially large skid surface for the .clinkers, coke and semi-burned fuel to slide from the main gnate and to discharge without material sticking. When viewing the interior of a furnace equipped with the extension grate of my invention one impressed by the relatively large smooth surface presented by the extension grate of my invention as compared with prior structures.

The forced draft air passages I4, l6 and I! in each of the grate bars are so dimensioned that the amount of material cut away to provide for the supplying of adequate draft through the extension grate does not materially interrupt the smooth flat surface over which the clinkers, coke and unburned fuel pass from the main grate. To secure this effect, I cast the grate bars with relatively wide walls so that the end to end distance between apertures I 4, l5 and IT in ad jacent grate bars is substantially equal to the transverse width of the apertures 14, I6 and IT. The spacing of the apertures or tuyere openings longitudinally of the grate bars is so selected that the distances between the apertures is substantially equal to the width of the apertures. By reason of this relationship, the smooth surface effect is obtained by the extension grate structure which is one of the striking features observed during the actual operation of the furnace.

Substantial surface area for the extension grate is maintained although adequate forced draft passages are provided through the surface area. The smooth surface area permits uniform progression of the clinkers, coke and unburned fuel from the main grate while sufficient draft under pressure is forced through the openings to maintain the extension grate at a safe temperature.

I have found the construction of extension grate described herein highly practical in manufacture and production and successful in operation and inexpensive in maintenance. However, I realize that modifications may be made in the shape and size of the bar and accordingly I intend no limitations upon my invention other than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a stationary extension grate, a multiplicity of longitudinally extending grate bars, each of said grate bars being constituted by an inverted channel shaped member having tuyre apertures extending through the active surface thereof, stationary upper and lower supports for said grate bars, a plane supporting portion for the upper end of each grate bar extending in a plane substantially at an angle with respect to the active surface of the extension grate and engaged with the upper support, and an upwardly recessed supporting portion at the lower end of each grate bar engaged with said lower support, the lower end of each extension grate bar being bifurcated on the exposed side thereof and operating to maintain the grate bar in position laterally with respect to said lower support.

2. In a stationary extension grate, a multiplicity of longitudinally extending grate bars, each of said grate bars being constituted by an inverted channel shaped member having tuyre apertures extending through the active surface thereof, stationary upper and lower supports for said grate bars, a plane supporting portion for the upper end'of each grate bar extending in a plane substantially at an angle with respect to the active surface of the extension grate and engaged with the upper support, and a supporting portion at the lower end of each grate bar engaged with said lower support, the lower end of I said grate bar being bifurcated on the exposed side thereof and being provided with an inner coacting downwardly projecting lug for forming interengaging means with said lower support for maintaining each grate bar in position.

3. In a stoker furnace, a stationary extension grate comprising a multiplicity of inclined longitudinally extending grate bars, each of said grate bars having a plane supporting portion at the upper end thereof and a recessed supporting portion at the lower end thereof and being constituted by a substantially channel shaped inverted section with the intermediate exposed wall thereof apertured for the passage of a forced draft of air, the side walls of each channel shaped grate bar tapering from a relatively wide intermediate position to each of the supporting ends thereof for effectively lowering the center of equilibrium of said inclined grate bar.

4. In a stoker furnace, a main grate, a stationary extension grate disposed at the lower end of the main grate and comprising a multiplicity of longitudinally extending grate bars, each of said grate bars being constituted by a substantially channel shaped inverted section with the intermediate rear wall thereof apertured for the passage of a forced draft of air, the side walls of each channel shaper grate bar tapering from a relatively wide intermediate position to each of the supporting ends thereof, stationary upper and lower supports for said grate bars, a plane supporting portion at the upper end of each grate bar extending on an axis substantially at an angle with the plane of the surface of said extension grate and engaged with the upper support, and a supporting portion at the lower end of each grate bar comprising a bifurcated portion and an intermediate projecting lug portion engaged with said lower support for maintaining the grate bar in position.

5. A furnace structure comprising in combination with a main grate, a stationary extension grate supported in inclined position at a substantially 45 angle adjacent the end of the main grate and comprising a multiplicity of parallel extending grate bars replaceably positioned adjacent each other, said bars having spacing members formed integral with the side walls thereof for providing passages for forced draft therebetween and conjointly presenting a flat plane surface, each of said extension grate bars having relatively wide wall portions and transversely disposed air passages, the transverse dimension of the air passages in said grate bars being substantially equal to the transverse end to end distance between the air passages in adjacent grate bars through said spacing members.

6. In a furnace structure, a stationary extension grate comprising a multiplicity of parallel extending grate bars supported in inclined position at a substantially 45 angle, each of said grate bars having a channel shaped inverted section with projections on the side walls thereof abutting face to face for providing passages for forced draft therebetween, said grate bars in combination having a substantially smooth fiat surface, the intermediate portions of said channel shaped sections each having transversely extending apertures therein spaced from each other in a longitudinal 5f, directional through distances substantially equal to the width of the apertures and being transversely spaced through said projections for distances substantially equal to the transverse dimension of the apertures, whereby a uniformly 10; apertured relatively smooth inclined surface is presented over which coke, coal and semi-burned fuel may be moved by gravitation from the main grate. 

